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The Long-Term Psychological Effects of Multiple Sex Partners

When it comes to the long-term effects of sex partners, less may be more.

Photographee eu/Shutterstock
Source: Photographee eu/Shutterstock

The mental health consequences of having multiple sex partners were long thought to include greater rates of anxiety and depression. At the same time, high rates of alcohol and substance abuse were thought to increase the chances of young adults engaging in unsafe sex with multiple partners. New research from a longitudinal study of over 1,000 New Zealanders suggests that, surprisingly, neither of these assertions is necessarily true.

The majority of studies citing a relationship between mental health problems, including substance and alcohol use, and one's number of sex partners are correlational in nature. As a result, it’s impossible to tell whether people seek sex partners in an effort to “self-medicate”—in other words, to reduce the emotional pain they are experiencing by seeking sexual connections with others, even if they are fleeting. The correlation-does-not-equal-causation problem in these studies also means that people with a high-risk lifestyle could seek sexual liaisons and substance use either because they have impulsive personalities or because they are anxious and depressed. The considered wisdom from such research, problematic as it was, led mental health experts to argue that in order to reduce the rates of risky sexual behavior, it’s necessary to treat the underlying psychological issues that lead individuals to these outlets for their unhappiness or personalities.

An international team of mental health researchers headed by Dunedin School of Medicine’s Sandhya Ramrakha and colleagues (2013) were uniquely positioned to test the causal directions of the multiple sex partner-mental health connections. The Dunedin Multidisciplinary Health and Development Study was begun in the mid-1970s with a cohort of over 1,000 children. They were followed every two years until they were 15 and then again at ages 18, 21, 26, and 32. An amazingly large percentage (96%) remained available for testing over that 30-year period. At ages 21, 26, and 32, they were given individual assessments on their mental health status in the areas of anxiety, depression, and substance (cannabis and/or alcohol) dependence. They were asked to report on the number of sex partners at each interval as well, allowing the researchers to compute the number of partners per year. With these data in hand, Ramrakha and team were able to calculate the odds of a participant developing a psychological disorder while controlling for earlier mental health problems at each test occasion.

For both men and women, taking into account prior psychological disorders, the odds of developing substance dependence increased virtually linearly with the number of sex partners. The relationship was particularly pronounced, however, for women. People having a higher number of sex partners did not have higher rates of anxiety or depression; the mental health associations were limited to substance use.

You might be wondering how multiple is "multiple" in the sex partner equation. The sample distribution led the researchers to divide the number of partners into three groups on a yearly basis: 0 or 1, 1.1-2.5, and 2.6 or over. However, some participants reported more than 10 in a given year.

The authors acknowledge that, even though they ruled out the effects of prior substance use on number of sex partners, the possibility remains that people living a risky lifestyle have a higher number of sex partners and, later on, develop mental health problems. It’s also possible that people who are having sex with multiple partners are in situations where alcohol and drugs are around, and therefore, will be the ones to develop substance dependence over time.

The nature of casual sex relationships may, however, present a risk factor in and of itself. These relationships may be particularly likely to be impersonal, lacking in the potential to provide emotional fulfillment. People having a string of these relationships may turn to the self-medication provided by alcohol or drugs. As the authors point out, drinking alcohol to cope with feelings of loneliness and despair can pave the way for later substance dependence.

Although women and men are developing similar patterns of sexual behavior and substance use, particularly in this cohort, the links were stronger for women, as I noted earlier. For women, having multiple sex partners still may go against what they regard as socially acceptable. They might cope with their feelings of shame, embarrassment, and perhaps dissatisfaction by turning to alcohol and drugs, setting them up for the future development of a substance use disorder.

The upshot of this fascinating study is that if you or someone you know is involved in a series of casual or fleeting relationships, there may be alcohol or drug dependence issues down the road. Women in particular might want to consider their reasons for becoming involved in frequent sexual pairings, and even more importantly, their feelings the morning after. The purpose of research such as this is not to scold people for having multiple partners or add to the guilt of those who already feel that they’re violating their own moral standards. Instead, it’s to point out that, from a strictly scientific standpoint, engaging in frequent sex with multiple partners does seem to be associated with risk.

The benefits of a long-term study that follows people over the critically formative early years of life is that we can learn about ways to prevent mental health problems for people as they navigate the stressful years of early adulthood. With this knowledge, young adults, along with their parents and counselors, can perhaps be better prepared to seek intervention and pave the way for a less troubled and more fulfilling life.

Copyright Susan Krauss Whitbourne, Ph.D. 2013


Ramrakha, S., Paul, C., Bell, M. L., Dickson, N., Moffitt, T. E., & Caspi, A. (2013). The relationship between multiple sex partners and anxiety, depression, and substance dependence disorders: A cohort study. Archives Of Sexual Behavior, doi:10.1007/s10508-012-0053-